O-rings can be used in place of shock cord for a cleaner look and tighter fit. Our U.V. resistant O-rings don?t break or deteriorate due to sun exposure. Simply push the O-ring part way through the sail tensioning loop, pull the ring through itself, and stretch the pulled end over the nock. O-rings can also be used to hold two intersecting spars together, such as a top spreader intersecting the spine on a stunt kite. Available in one size.